1. Field of the Invention
The present invention relates to a development roller (hereinafter simply referred to as a “roller” in some cases), and more particularly relates to a development roller used in a development process performed by an image forming device using an electrophotographic system.
2. Description of the Related Art
In an image forming device, such as a copying machine or a printer, using an electrophotographic system, roller members having conductivity are used in individual electrophotographic processes, such as development, electrification, and transfer (toner supply and cleaning).
Heretofore, as conductive rollers used as a development roller, an electrification roller, a transfer roller (toner supply and cleaning) and the like, a basic structure has been used in which a conductive elastic layer composed of a conductive rubber, high molecular weight elastomer, high molecular weight foam, or the like, which has conductivity obtained by using a conductive agent, is formed around the periphery of a conductive metal shaft, and in addition, on the periphery of this basic structure thus formed, at least one coating film is provided in order to obtain a desired surface roughness, conductivity, hardness, and the like.
The conductive roller thus described is formed in general by applying paint onto the surface of the elastic layer formed around the periphery of the metal shaft. However, when the coating film is formed on the elastic layer, depending on the solvent resistance thereof, the surface of the elastic layer may be dissolved with a solvent contained in the paint, and as a result, the desired surface roughness of the roller to be finally obtained may not be ensured in some cases.
In order to overcome the above problem, as a technique for eliminating the adverse influence of a solvent on the elastic layer by forming a coating film thereon using a water-based paint, for example, the following technique has been disclosed in Japanese Patent No. 2996846 (claims, paragraph [0005] etc). According to this technique, in a composite roller in which a surface coating film formed from a paint composed of an organic solvent and an organic compound dissolved therein is provided on the surface of a roller body, the surface being composed of a foam made from an organic compound having solubility or swelling properties to an organic solvent, a coating film formed from a mixed solution containing a predetermined organic compound and a water medium is provided as a solvent blocking film against the organic solvent of the paint forming the surface coating film between the roller body and the surface coating film so as to prevent the dissolution and swelling of the roller body which are caused by the organic solvent of the paint forming the surface coating film, and as a result, a composite roller having a smooth surface is obtained. In addition, in Japanese Unexamined Patent Application Publication No. 9-146340 (claims etc.), an electrification member has been disclosed in which a conductive layer formed from a water-based resin and a urethane modified acrylic resin layer are formed on the surface of an elastic foam layer in that order.
As described in the patent documents described above, by forming the coating film from a water-based paint on the elastic layer, the solvent blocking properties can be ensured, and as a result, for example, the surface of the elastic layer can be prevented from being roughened. However, according to the water-based resins which have been investigated, adhesion between the elastic layer and the coating film of the water-based paint is not sufficient in particular in the case of a roller such as a development roller which is driven by itself, and as a result, the coating film is disadvantageously peeled away during a continuous long operation.